Amino‐substituted 2‐Azaallenium Salts

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Abstract
Nitrilium salts (14a – i) react with imines (15a – e) to afford the mono‐ to tetraaza‐substituted 2‐azaallenium salts 16a – w in high yields. The stereochemistry of these compounds is discussed in terms of an allenic geometry (A) and a planar 1,3‐diaza‐1,3‐butadienium structure (B), respectively. According to the IR, 1H and 13C NMR spectra, the azaallenium salts 16 are rather flexible around the central nitrogen atom. In solution at least 16a – d assume chiral conformations similar to those of allenes. By DNMR measurements barriers to hindered rotation around the CN+C axis were found to range from δG173† = 36 ± 1 kJmol–1 for 16a to more than 90 kJmol–1 for 16c. According to an X‐ray structural analysis, 16o crystallizes in an almost perfect allene geometry (A). – Some interesting 13C‐14N couplings of the nitrilium salts 14 are reported.

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